Surveillance

The incidence of chickenpox has changed over the last 15 years with the introduction of chickenpox vaccine and new immunization recommendations and requirements. The Minnesota Department of Health (MDH) implemented chickenpox and shingles surveillance in the fall of 2005 pursuant to the Minnesota Communicable Disease Reporting Rule, (Chapter 4605).

Reporting

Schools are to report to MDH:

All suspect or confirmed cases of chickenpox in students and/or staff.

Prevention and Control in Schools

Exclude students or staff with chickenpox from school until all lesions have crusted. This is usually 4-7 days (typically 6 days) after the rash began.

Chickenpox can occur in vaccinated persons. This is referred to as “breakthrough infection” and is usually less severe, with an atypical presentation. Macules and papules rather than vesicular lesions may be present. Breakthrough cases should be considered infectious. Lesions may not crust; therefore, these cases should be excluded until all lesions have faded or no new lesions have occurred within a 24-hour period, whichever is later. Lesions do not need to be completely resolved before the individual is allowed to return to school.

Chickenpox outbreaks

An outbreak of chickenpox is defined as:

Five or more cases within a 2-month period in persons less than 13 years of age, or

Three or more cases within a 2-month period in persons 13 years of age and older.

Steps to take when a school outbreak of chickenpox occurs:

1.

Call MDH to report the beginning of an outbreak at 651-201-5414 or
1-877-676-5414.

Notify and inform parents and school staff that a chickenpox outbreak is occurring, and provide them information about chickenpox. A chickenpox fact sheet for the general public and one more specific to parents of school-age children are available on the MDH Varicella (Chickenpox) Basics MDH website.

4.

Identify and notify susceptible individuals. Susceptible students are those without documented history of chickenpox disease who are unvaccinated, vaccinated with only one dose, or whose immunization status is unknown.

Recognizing that not all grade cohorts have yet been required to receive two doses of chickenpox vaccine, it is prudent in the event of an outbreak to recommend the following:

•

Two doses of chickenpox vaccine for individuals who have no history of chickenpox disease and are unvaccinated.

•

A second dose of chickenpox vaccine for individuals who have received only one dose of vaccine, provided the appropriate interval has passed since the first dose (i.e., 3 months for children aged 12 months-12 years and 4 weeks for persons 13 years and older).

The national Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC) recommend that during school-based outbreaks of varicella, individuals who lack evidence of immunity and are not up-to-date on vaccination (i.e., 2 doses) be excluded from school. (Prevention of Varicella, Recommendations of the Advisory Committee on Immunization Practices MMWR June 22, 2007 / 56(RR04);1-40)
School exclusion of susceptible individuals may be indicated in certain situations. Please consult with MDH staff when an outbreak is identified in your school.

5.

Identify and notify individuals who meet any of the following criteria:

•

High risk for complications, including those who are:

•

Immunocompromised

•

15 years of age and older

•

Pregnant women
(Note: Varicella exposure during pregnancy is of concern only if the mother is susceptible to chickenpox.)

High-risk persons should contact their health care provider to determine if vaccination, immune-status testing, post-exposure prophylaxis or school exclusion is indicated.

The role of the health care provider

The local medical community should be notified if a varicella outbreak is occurring, particularly if an outbreak notification is disseminated broadly. MDH and your local public health department can facilitate this communication. This allows providers to prepare for possible increased calls from patients. MDH can assist with contacting health care providers.

Health care provider evaluation and diagnosis are not required for school surveillance and reporting purposes.

Health care providers may want their patients (or parents) to notify them if they develop chickenpox. However, most cases of chickenpox are not seen in the clinic unless clinically necessary.